/* Lzlib - Compression library for the lzip format
   Copyright (C) 2009-2020 Antonio Diaz Diaz.

   This library is free software. Redistribution and use in source and
   binary forms, with or without modification, are permitted provided
   that the following conditions are met:

   1. Redistributions of source code must retain the above copyright
   notice, this list of conditions, and the following disclaimer.

   2. Redistributions in binary form must reproduce the above copyright
   notice, this list of conditions, and the following disclaimer in the
   documentation and/or other materials provided with the distribution.

   This library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
*/

static int LZd_try_verify_trailer( struct LZ_decoder * const d )
  {
  Lzip_trailer trailer;
  if( Rd_available_bytes( d->rdec ) < Lt_size )
    { if( !d->rdec->at_stream_end ) return 0; else return 2; }
  d->verify_trailer_pending = false;
  d->member_finished = true;

  if( Rd_read_data( d->rdec, trailer, Lt_size ) == Lt_size &&
      Lt_get_data_crc( trailer ) == LZd_crc( d ) &&
      Lt_get_data_size( trailer ) == LZd_data_position( d ) &&
      Lt_get_member_size( trailer ) == d->rdec->member_position ) return 0;
  return 3;
  }


/* Return value: 0 = OK, 1 = decoder error, 2 = unexpected EOF,
                 3 = trailer error, 4 = unknown marker found,
                 5 = library error. */
static int LZd_decode_member( struct LZ_decoder * const d )
  {
  struct Range_decoder * const rdec = d->rdec;
  State * const state = &d->state;
  unsigned old_mpos = rdec->member_position;

  if( d->member_finished ) return 0;
  if( !Rd_try_reload( rdec ) )
    { if( !rdec->at_stream_end ) return 0; else return 2; }
  if( d->verify_trailer_pending ) return LZd_try_verify_trailer( d );

  while( !Rd_finished( rdec ) )
    {
    int len;
    const int pos_state = LZd_data_position( d ) & pos_state_mask;
    const unsigned mpos = rdec->member_position;
    if( mpos - old_mpos > rd_min_available_bytes ) return 5;
    old_mpos = mpos;
    if( !Rd_enough_available_bytes( rdec ) )	/* check unexpected EOF */
      { if( !rdec->at_stream_end ) return 0;
        if( Cb_empty( &rdec->cb ) ) break; }	/* decode until EOF */
    if( !LZd_enough_free_bytes( d ) ) return 0;
    if( Rd_decode_bit( rdec, &d->bm_match[*state][pos_state] ) == 0 ) /* 1st bit */
      {
      /* literal byte */
      Bit_model * const bm = d->bm_literal[get_lit_state(LZd_peek_prev( d ))];
      if( St_is_char( *state ) )
        {
        *state -= ( *state < 4 ) ? *state : 3;
        LZd_put_byte( d, Rd_decode_tree8( rdec, bm ) );
        }
      else
        {
        *state -= ( *state < 10 ) ? 3 : 6;
        LZd_put_byte( d, Rd_decode_matched( rdec, bm, LZd_peek( d, d->rep0 ) ) );
        }
      continue;
      }
    /* match or repeated match */
    if( Rd_decode_bit( rdec, &d->bm_rep[*state] ) != 0 )	/* 2nd bit */
      {
      if( Rd_decode_bit( rdec, &d->bm_rep0[*state] ) == 0 )	/* 3rd bit */
        {
        if( Rd_decode_bit( rdec, &d->bm_len[*state][pos_state] ) == 0 )	/* 4th bit */
          { *state = St_set_short_rep( *state );
            LZd_put_byte( d, LZd_peek( d, d->rep0 ) ); continue; }
        }
      else
        {
        unsigned distance;
        if( Rd_decode_bit( rdec, &d->bm_rep1[*state] ) == 0 )	/* 4th bit */
          distance = d->rep1;
        else
          {
          if( Rd_decode_bit( rdec, &d->bm_rep2[*state] ) == 0 )	/* 5th bit */
            distance = d->rep2;
          else
            { distance = d->rep3; d->rep3 = d->rep2; }
          d->rep2 = d->rep1;
          }
        d->rep1 = d->rep0;
        d->rep0 = distance;
        }
      *state = St_set_rep( *state );
      len = min_match_len + Rd_decode_len( rdec, &d->rep_len_model, pos_state );
      }
    else					/* match */
      {
      unsigned distance;
      len = min_match_len + Rd_decode_len( rdec, &d->match_len_model, pos_state );
      distance = Rd_decode_tree6( rdec, d->bm_dis_slot[get_len_state(len)] );
      if( distance >= start_dis_model )
        {
        const unsigned dis_slot = distance;
        const int direct_bits = ( dis_slot >> 1 ) - 1;
        distance = ( 2 | ( dis_slot & 1 ) ) << direct_bits;
        if( dis_slot < end_dis_model )
          distance += Rd_decode_tree_reversed( rdec,
                      d->bm_dis + ( distance - dis_slot ), direct_bits );
        else
          {
          distance +=
            Rd_decode( rdec, direct_bits - dis_align_bits ) << dis_align_bits;
          distance += Rd_decode_tree_reversed4( rdec, d->bm_align );
          if( distance == 0xFFFFFFFFU )		/* marker found */
            {
            Rd_normalize( rdec );
            if( (unsigned)rdec->member_position - old_mpos > rd_min_available_bytes )
              return 5;
            if( len == min_match_len )		/* End Of Stream marker */
              {
              d->verify_trailer_pending = true;
              return LZd_try_verify_trailer( d );
              }
            if( len == min_match_len + 1 )	/* Sync Flush marker */
              {
              rdec->reload_pending = true;
              if( Rd_try_reload( rdec ) ) { old_mpos += 5; continue; }
              else { if( !rdec->at_stream_end ) return 0; else break; }
              }
            return 4;
            }
          }
        }
      d->rep3 = d->rep2; d->rep2 = d->rep1; d->rep1 = d->rep0; d->rep0 = distance;
      *state = St_set_match( *state );
      if( d->rep0 >= d->dictionary_size ||
          ( d->rep0 >= d->cb.put && !d->pos_wrapped ) ) return 1;
      }
    LZd_copy_block( d, d->rep0, len );
    }
  return 2;
  }
